Field of the Invention
This invention relates in general to a method and apparatus for predrying coal which is to be infused in a coke oven battery, particularly to a new and useful method for operating coke batteries in association with a predrying or preheating plant for the coal to be coked and wherein the moist charge coal is preheated and predried by bringing it into contact with a circulated amount of hot inert gas to remove water from the charge coal and wherein the inert gas comprises a gas containing only a small amount of oxygen and a remainder comprising nitrogen, carbon dioxide and steam and wherein the preheated and predried coal is charged into the coke oven and the coke oven gases which are generated are directed out through an offtake and an amount of steam approximately equal to the amount of water removed from the charge coal is added to the coke oven gases in the offtake.
The predrying or preheating of coking coals has prevailed in the coke industry quite generally, because such an operation makes it possible to produce good metallurgical coke even from coals which, without this preliminary statement, would not give a usable coke, which means that the range of the types of coal yielding a metallurgical coke of satisfactory quality is thereby enlarged.
In addition, the preliminary heating of coke coal reduces the time necessary for carbonization by the period of time needed for vaporizing the moisture adhering to the coke coal, which period may amount of a fourth or fifth or even more of the entire coking time. In this way, the high expenses of the preheating operation are partly compensated.